Conventional innerspring units for a mattress are typically constructed of a great number of identical and substantially helical-shaped coils that resemble springs, which are uniformly disposed in rows and columns over the entire area of the innerspring unit. The level of support and comfort provided by a mattress, often referred to as "firmness," is a function of both the filling and padding materials on the top and bottom of the innerspring unit and the performance characteristics of the coils. Since the identical coils of a conventional innerspring are uniformly disposed over the entire area of the innerspring, the resulting mattress will have substantially constant support characteristics over the entire area of the mattress. In other words, the level of support provided at one location will be the same as the level of support provided at another location.
The edge support provided by a conventional mattress designed with an innerspring formed from coils is usually inadequate due to the inherent physical characteristics of a coil. A coil is symmetric about its central axis and therefore must be inset to avoid extending beyond the edge of the innerspring unit. As a result, support at the edge of the innerspring is provided merely by the edge of the coil, which is significantly less firm and has a tendency to "tip" or deflect sideways when pressure is applied.
In many cases a constant level of support is not a desirable feature of a mattress. For example, the force applied to a mattress by a prone human body varies depending upon the particular portion of the body which is considered. A human torso will usually exert considerably greater force on the mattress than a leg, foot, or head. A conventional mattress design will, however, provide the same support for all areas of the body, which in some cases may lead to discomfort. Furthermore, most king- and queen-sized mattresses are designed to accommodate two individuals in a prone position. Since one individual may have a dramatically different physical profile and weight characteristics than the other individual, a conventional mattress may provide one individual with a dramatically different, and likely undesirable, comfort level than the other individual.
Conventional mattress innerspring units are designed with a great number of coils. For example, an innerspring for a king-sized mattress may use more than 1000 identical coils for support. Such a design can be undesirably heavy, as well as extraordinarily complicated, expensive and difficult to manufacture and assemble. Due to the great number of coils needed to provide adequate support for a conventional mattress, it is impractical to even consider varying the type or location of coils disposed throughout the innerspring. Moreover, in order to efficiently and cost-effectively manufacture a conventional innerspring, high speed automated equipment is required which repetitively selects, positions and affixes the identical coils uniformly throughout the area between the wire grids.
U.S. Pat. No. 3,561,021 to Slominski (Feb. 9, 1971) discloses an innerspring design that uses formed wires for support. Slominski is directed to a design fabricated by assembling a plurality of identical elongated modules in a side-by-side relation to the desired width of the unit. It is apparent that the Slominski design was not met with success, likely because of its inability to provide adequate lateral stability. Furthermore, Slominski teaches fabrication from identical formed wire elements, which results in a mattress, similar to conventional coil mattresses, that provides constant support throughout the entire area of the mattress.